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Equilibrium

Total questions: 80

Worksheet time: 2hrs 44mins

Name
Class
Date
1.

What are the two factors to look for when determining if the reaction is at equilibrium?

a)

Forward reaction rate is faster than the reverse and concentrations are equal

b)

Forward and reverse reaction rates are equal and concentration is constant

c)

Forward and revers reaction rates are equal and concentration is equal

d)

Forward reaction rate is faster than the reverse and concentration is equal

2.
This symbol indicates that a reaction is ____________
a)
reversible
b)
irreversible
3.

When the rate of the forward reaction is equal to the rate of backward reaction, the system is said to be in

a)

Dynamic Equilibrium

b)

Chemical Balance

c)

Chemical Constant

d)

Chemical Reaction

4.
At what time the reaction reached equilibrium?
a)
t1
b)
t2
c)
t3
d)
t4
5.
It is a chemical reaction where the reactants form products that, in turn, react together to give the reactants back.
a)
reversible reaction
b)
irreversible reaction
c)
decomposition reaction
d)
synthesis
6.
Identify the labels (a) and (b) on the graph.
a)
a is concentration of reactants and b is the concentration of product
b)
a is concentration of product and b is the concentration of reactant
c)
a is the volume of reactants and b is the volume of product
d)
a the mass of reactants and b is the mass of product
7.
Define chemical equilibrium.
a)
A reaction is reversible.
b)
The concentration of the reactants is equal to the concentration of the products.
c)
The rate of a forward reaction is equal to the rate of the reverse reaction.
d)
The reaction stops and no further change in concentration occurs.
8.
At what time (in seconds) is equilibrium established?
a)
0 seconds
b)
1 second
c)
5 seconds
d)
10 seconds
9.
Which of the two graphs reaches equilibrium?
a)
The left one.
b)
The right one.
c)
Both of them.
d)
Neither.
10.
During equilibrium, the rates of the forward and the reverse reaction are ________
a)
the same 
b)
unequal
c)
unequal for exothermic reactions
d)
unequal for endothermic reactions
11.
How does a catalyst change during a reaction?
a)
It is part of the products
b)
It combines with the reactants
c)
It precipitates
d)
It remains unchanged
12.
How do catalysts increase the rate of reaction?
a)
The frequency of collisions is the increased
b)
the activation energy is lowered
c)
the energy of collisions is increased
d)
Both the frequency and energy of collisions is increased
13.
What is the activation energy?
a)
the quantity of heat absorbed in a reaction
b)
the minimum energy needed to begin a reaction
c)
the energy given off after reactants collide.
d)
both the energy and frequeny of collisions in increased
the energy difference between reactants and products
14.
When the system X + 2 Y <=> Z has reached equilibrium, which of the following is TRUE?
a)
Forward reaction and Backward reaction stop.
b)
Forward reaction has sped up and backward reaction has slowed down.
c)
Forward and backward reactions occur at the same rate.
d)
Forward reaction has slowed down and backward reaction has sped up.
15.
Le Chatelier's Principle states that.... 
If a (dynamic) equilibrium is disturbed by changing the conditions, the position of equilibrium................
a)
moves to increase the change
b)
moves to counteract the change
c)
does not change
16.
What are [A] and [B]?
a)
concentration of reactants
b)
concentration of products
c)
energy of reactants
d)
energy of products
17.
2A + 3B  <---->  2AB
The forward reaction points towards the __________.
a)
left
b)
right
c)
up
d)
down
18.
2A + 3B  <---->  2AB
The forward reaction forms the substance __________.
a)
A
b)
B
c)
AB
d)
A + B
19.
2A + 3B  <---->  2AB
The reverse reaction points towards the __________.
a)
left
b)
right
c)
up
d)
down
20.
2A + 3B  <---->  2AB
The reverse reaction forms the substance __________.
a)
A
b)
B
c)
AB
d)
A + B
21.
Changes in pressure will only affect substances that are in the __________ state.
a)
gaseous
b)
liquid
c)
solid
d)
plasma
22.
If a reaction is reversible and has reached equilibrium, what can be said about the amounts of reactants and products?
a)
some reactant, some product
b)
no reactant, all product
c)
all reactant, no product
23.
The following factors affect the position of equilibrium EXCEPT
a)
Concentration
b)
Pressure
c)
Temperature
d)
States of matter
24.

What kind of reaction is this?

a)

Endothermic

b)

Exothermic

25.
Le Chatelier's Principle states that if a chemical system at equilibrium is stressed,
a)
the system will adjust to increase the stress
b)
the system will adjust to reduce the stress
c)
the system will not adjust
26.
True or False: All reactions are reversible
a)
True
b)
False
27.
In an exothermic reaction, heat is ...
a)
taken in
b)
given out
28.
In an endothermic reaction, heat is 
a)
taken in
b)
given out
29.
A substance that increases speed of chemical reaction without being being changed is called:
a)
Catalyst
b)
Acid
c)
Base
d)
pressure
30.
Increase in temperature of the reactants can do one of the following
a)
Slow collision frequency
b)
Allow less effective collision between the particles
c)
Cause particles to lose speed
d)
Increase collision between the particles thus increasing the rate.
31.
The amount of a substance in a given volume.
a)
concentration
b)
temperature
c)
surface area
d)
catalyst
32.
Exposing more particles for collisions is an increase in 
a)
concentration
b)
surface area
c)
temperature
d)
catalyst
33.
Which of the following slows down the rate of a chemical reaction?
a)
Place the reactants in hot water
b)
Place the products in ice bath
c)
Place the reactants in a ice bath
d)
Keep stirring the reactants with a stirring rod
34.
If more reactants are used in a chemical reaction, more products will be produced. This is because
a)
More reactants cause the reaction to heat up
b)
More reactants take up the same volume
c)
More reactants have more atoms to react to form more products
d)
Too many products can slow down the reaction
35.
In a chemical reaction, if the reactants are heated, the reaction usually happens
a)
Faster
b)
Slower
c)
At the same rate
d)
In a smaller volume
36.
Some chemical reactions require a substance called a catalyst. The main purpose of a catalyst is
a)
To warm up the reaction
b)
To speed up the reaction
c)
To create more reactants
d)
To stop the reaction
37.
During equilibrium, the rates of the forward and the reverse reaction are ________
a)
the same 
b)
unequal
c)
unequal for exothermic reactions
d)
unequal for endothermic reactions
38.
The idea that when a system at equilibrium is stressed, it will react to relieve that stress and return to equilibrium is known as:
a)
Boyle's Law
b)
Le Chatelier's Principle
c)
Charles Law
d)
Denninger's Law
39.

Which statements about reversible reactions are correct?

1 An increase in concentration of a reactant always increases the concentration of the product.

2 An increase in temperature always increases the rate at which the equilibrium is established.

3 An increase in temperature always increases the concentration of the product at equilibrium.

a)

1, 2 and 3 are correct

b)

1 and 2 only are correct

c)

2 and 3 only are correct

d)

1 only is correct

40.

A chemical equilibrium may be established by starting a reaction with __________

a)

reactants only.

b)

products only.

c)

equal quantities of reactants and products.

d)

any quantities of reactants and products.

e)

all the above

41.

Which of the following is true for a chemical reaction at equilibrium?

a)

only the forward reaction stops

b)

only the reverse reaction stops

c)

both the forward and reverse reactions stop

d)

the rate constants for the forward and reverse reactions are equal

e)

the rates of the forward and reverse reactions are equal

42.

A complete reaction is in which:

a)

All the reactants convert into products

b)

All the reactants do not convert into products

c)

Half reactants convert into products

d)

only 10% reactants convert into products

43.
At equilibrium the concentration of all species in the reaction is _________.
a)
Constant
b)
Increasing
c)
Decreasing
d)
Oscillating
44.
B represents
a)
energy absorbed
b)
energy released
c)
activation energy
45.

Which statement correctly describes an endothermic chemical reaction?

a)

The products have lower potential energy than the reactants, and the ΔH is positive

b)

The products have lower potential energy than the reactants, and the ΔH is negative

c)

The products have higher potential energy than the reactants, and the ΔH is positive

d)

The products have higher potential energy than the reactants, and the ΔH is negative

46.
Le Chatelier's Principle states that.... 
If a (dynamic) equilibrium is disturbed by changing the conditions, the position of equilibrium................
a)
moves to increase the change
b)
moves to counteract the change
c)
does not change
47.
What is Kc for the following reaction? 
   2 NO(g)  +  O2(g) ⇌ 2 NO2(g)
a)
Kc = [NO2]2 / [NO]2 [O2]
b)
Kc =  [NO]2[O2] / [NO2]2
c)
Kc = [NO2]2 / [NO]2[O2]
d)
Kc = 2[NO][O2] / 2[NO2]
48.

Which of the following is TRUE for a system that is in dynamic equilibrium?

a)

The forward reaction goes to 100% completion.

b)

The reaction rate of the forward reaction approaches zero.

c)

The concentration of products is equal to the concentration of the reactants.

d)

none of the above

49.

Which of the following is TRUE about a chemical system in equilibrium?

a)

Temperature changes have no effect on reaction rate.

b)

Addition of more reactants have no effect on reaction rate

c)

Reaction rate remains stable as long as temperature and pressure are stable.

d)

none of the above

50.
Why does increased concentration increase the rate of reaction?
a)
the activation energy is lowered
b)
collisions occur with greater energy
c)
the frequency of collisions is increased
51.

Why does the rate of the reaction decrease over time?

a)

Exothermic reactions lose heat which cools the reaction which decreases reaction rate.

b)

As the reaction proceeds, the concentration of the products results in fewer collisions

c)

As the reaction proceeds, a decrease in the concentration of reactants results in fewer successful collisions.

d)

Not all molecules will react and some choose to stay in their present form

52.

When writing the expression for an equilibrium constant, which type of substance is included?

a)

solids

b)

pure liquids

c)

gases

d)

all of the above

53.

Given the reaction:

CH4(g) + 2O2(g) --> 2H2O(g) + CO2(g)

What is the overall result when CH4(g) burns according to this reaction?

a)

Energy is released and the ΔH is positive

b)

Energy is released and the ΔH is negative

c)

Energy is absorbed and the ΔH is positive

d)

Energy is absorbed and the ΔH is negative

54.

Which statement correctly describes an endothermic chemical reaction?

a)

The products have lower potential energy than the reactants, and the ΔH is positive

b)

The products have lower potential energy than the reactants, and the ΔH is negative

c)

The products have higher potential energy than the reactants, and the ΔH is positive

d)

The products have higher potential energy than the reactants, and the ΔH is negative

55.

Given the reaction


S(s) + O2(g) --> SO2(g) + energy


Which diagram best represents the potential energy changes for this reaction?

a)

a

b)

b

c)

c

d)

d

56.

Given the potential energy diagram for the chemical reaction:


Which statement correctly describes the energy changes that occur in the forward reaction

a)

The activation energy is 50kJ and the reaction is exothermic

b)

The activation energy is 50kJ and the reaction is endothermic

c)

The activation energy is 10kJ and the reaction is exothermic

d)

The activation energy is 10kJ and the reaction is endothermic

57.

Which statement best explains the role of a catalyst in a chemical reaction?

a)

A catalyst changes the kinds of products produced

b)

A catalyst provides an alternate reaction pathway that requires less activation energy

c)

A catalyst limits the amount of reactants used

d)

A catalyst is added as an additional reactant and is consumed but not regenerated

58.

2 SO2(g) + O2(g) ↔ 2 SO3(g) When 0.40 mole of SO2 and 0.60 mole of O2 are placed in an evacuated 1.00-liter flask, the reaction represented above occurs. After the reactants and the product reach equilibrium and the initial temperature is restored, the flask is found to contain 0.30 mole of SO3. Based on these results, the expression for the equilibrium constant, Kc, of the reaction is

a)
b)
c)
d)
59.
An equilibrium constant with a large magnitude indicates…
a)
A very fast reaction
b)
More products at equilibrium
c)
More reactants at equilibrium
d)
nothing, without considering the stoichiometry of the reaction
60.
Consider the following reaction :    
SO2 (g) +  NO2 (g) ↔ SO3 (g) + NO (g)  
had reached a state of equilibrium, was found to contain   0.40 M SO3 , 0.30 M NO, 0.15 M NO2 , and 0.20 M SO2. Calculate the equilibrium constant  for this reaction.
a)
4
b)
.42
c)
.25
d)
1
61.
The following graph shows two different reaction pathways for the same overall reaction at the same temperature. Which pathway is slower and why?
a)
Red, because the activation energy is larger
b)
Blue, because the activation energy is lower
c)
both reaction progress at the same rate
62.

What does the M after a concentration value stand for?

a)

meters

b)

music

c)

Molarity

d)

moles

63.
T/F: At equilibrium, the amount of reactants and products are the same.
a)
True
b)
False
64.
T/F: At equilibrium, the rate of transfer between the reactants and products is unequal.
a)
True
b)
False
65.
T/F: At equilibrium, the rate of transfer between the reactants and products is equal.
a)
True
b)
False
66.
T/F: A reaction must start with the same amount of reactants as products to reach equilibrium.
a)
True
b)
False
67.
What time is equilibrium reached?
a)
0 s
b)
2000 s
c)
6000 s
68.
What are the two types of stresses that can shift equilibrium?
a)
Concentration and Catalyst
b)
Concentration and Temperature
c)
Catalyst and Temperature
69.
This substance speeds up the rate of a chemical reaction without being consumed or changed.
a)
intermediate
b)
catalyst
c)
reactant
d)
product
70.
Consider: 2H2 + O2 -> 2H2O
What is the ratio of the initial appearance of water to the initial disappearance of oxygen?
a)
1:1
b)
2:1
c)
1:2
d)
2:2
71.
For the reaction...
SO2 + O2  <=>  SO3
If the concentration of SO2 is increased, the equilibrium position of the reaction will shift ___________.
a)
to the left
b)
to the right
c)
to the left and right 
d)
neither left nor right
72.
For the reaction...
N2  +  O2  <=>  2NO
If  O2 is removed, the  concentration of N2 will _______.
a)
increase
b)
decrease
c)
remain the same
d)
double
73.
For the reaction...
SO2 + O2 <−>  SO3
If the equilibrium shifts to the right, the concentration of O2 will ___________.
a)
increase
b)
decrease
c)
remain the same
d)
double
74.
For the reaction...
SO2 + O2 <−>  SO3
If the equilibrium shifts to the right, the concentration of SO3 will ___________.
a)
increase
b)
decrease
c)
remain the same
d)
double
75.
For the reaction...
SO2 + O2 <−>  SO3
If the equilibrium shifts to the left, the concentration of SO3 will ___________.
a)
increase
b)
decrease
c)
stay the same
d)
triple
76.
For the reaction...
heat  +  N2  +  O2  <−>  2NO
If  O2 is removed, the  concentration of N2 will _______.
a)
increase
b)
decrease
c)
remain the same
d)
double
77.
For the reaction...
heat  +  N2  +  O2  <−>  2NO
If  NO is removed  from the system, the concentration of N2 will _______.
a)
increase
b)
decrease
c)
remain the same
d)
double
78.
For the reaction...
H2 (g)  + Cl2 (g) <−>  2HCl (g)  +  heat
If the temperature is cooled, the _________ reaction will be favored.
a)
forward
b)
reverse
c)
forward and reverse
79.
For the reaction...
N2 (g) +  3 H2 (g) <−> 2 NH3 (g)

If the pressure in the system is increased,  _______ reaction will be favored.
a)
 the forward
b)
the reverse
c)
neither
80.
For the reaction...
H2 (g)  + Cl2 (g) <−>  2HCl (g)  +  heat
If the pressure in the system is increased, the equilibrium will _______.
a)
shift left
b)
shift right
c)
not shift

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